Basalt is an abundant igneous rock formed from by lava cooling on the earth's surface. Though the composition of basalt varies, basalt typically is comprised of 45-55 wt. % silica (SiO2), 2-6 wt. % total alkalis, 0.5-2.0 wt. % titanium dioxide (TiO2), 5-14 wt. % iron oxides, and 14 wt. % or more (Al2O3). Contents of calcium oxide (CaO) are typically around 10 wt %, and magnesium oxide (MgO) typically ranges 5 to 12 wt %. The composition of Basalt can also be describe in terms of its mineral compositions which include amphibole, pyroxene, feldspar, plagioclase feldspar, feldspathoids, augite, and olivine.
Basalt can be melted and processed into a fiber. Basalt rock is plentiful and inexpensive, however a great deal of energy is required to melt the basalt rock and form it into a fiber. Conventional basalt fibers may not be suitable for certain applications due to the prevalence of defects which cause the fibers to break. Defects, including fissures and inclusions, result in weaker areas of the fiber. These weak areas of the fiber are prone to breaking not only during the fiber manufacturing process, but also during the manufacture of end products.
Conventional basalt fibers can be made using gas furnaces. For example U.S. Pat. No. 6,125,660 to Gorobinskaya, et al., discloses a method of using a gas furnace to melt basalt at a temperature of 1300° C. to 1450° C. The gas furnace is lined with a refractory material which resists heat.
Another example of producing a conventional basalt fiber is found in U.S. Pat. No. 8,042,363 to Kibol, et al. This patent discloses a method of producing basalt fibers of various chemical compositions using a gas furnace with a temperature ranging from 1400° C. to 2000° C. Another example of producing a basalt fiber is found in U.S. Pat. No. 8,042,362 to Kibol, et al. This patent discloses a specialized apparatus for processing a basalt melt. The furnace is heated using natural gas by means of gas-air burners at a temperature above 1500° C. and the furnace is lined with refractory materials. The basalt is melted in an oxidative medium with excess air supplied by blowers. The process results in the generation of combustion gases including poisonous carbon monoxide and the greenhouse gas carbon dioxide.